The effect of an electrical corona discharge upon the reaction of SO2 to SO3 in low concentration SO2 - air mixtures

An investigation of a pilot plant electrical dust precipitator was conducted to determine its ozone generating characteristics in air as well as the ability of the ozone formed to convert gaseous SO2 to particulate SO3. It was anticipated that in addition to the known primary particulate dust and mist removal function of a precipitator, a secondary gaseous removal facility was inherent in its operation. Ozone formation quantities were determined at varied air flow and electrical power input levels to the precipitator. Maximum ozone generation was 0.02 pounds per hour at an energy input level of 113 KW-HR per pound - approximately one-seventh the efficiency of commercial ozonators. Conversion of gaseous SO2 to particulate SO3 by the ozone generated in the precipitator was determined at varied SO2 concentration levels and air flow rates. Two definite reactions were observed in the formation of SO3 from SO2 by ozone. At SO2 concentrations below 100 P.P.M. five mols of O3 are required per mol of SO3 formed whereas above SO2 concentrations of 400 P.P.M. one mol of ozone produced three mols of SO3. An evaluation of the results obtained indicates that a commercial electrical dust precipitator is an impractical device for reducing gaseous SO2 by reaction of generated ozone to form particulate SO3. While 100% of the generated ozone can convert gaseous SO2 to particulate SO3, the SO2 concentration levels required for the reaction are such that less than 1% of the total SO2 is removed from the gas stream